1. Field of the Invention
The invention concerns a mobile working machine, in particular a mobile concrete pump with a chassis, with two forward and two rearward support struts extendable out from a transport position into at least one supporting position and each preferably supportable upon a surface by a telescopic supporting jack, with a working boom, preferably a concrete distribution boom, which can be extended out of a transport position and into working positions that project beyond the chassis and which can rotate about a vertical axis fixed relative to the chassis, with sensors or measurement devices in the area of the support jacks for determining the respective support load and with a support safety monitoring device receiving the output signals from the sensors or measuring devices.
2. Description of the Related Art
Mobile working machines of this type are provided with extendable support struts, which are intended to enhance the stability of the working device at the location of employment. The support struts have for their part the task of removing the spring-support of the vehicle and to remove the load from the wheels. On the other hand, the support struts are designed to minimize the danger of tipping, which result when high tip moments are produced by the working boom. The support feet of the support struts thereby form the corners of a quadrilateral, of which the side edges define a surface within which the center of gravity of the work device must lie, in order to guarantee a stable stance. Since the projecting work boom is rotatable, the center of gravity describes a full circle during turning, which must lie within the quadrilateral over the work area of the work boom. Since the space in construction sites may be confining, it is often not possible to completely extend the support struts. Thereby the freedom of rotation of the work boom becomes limited. In order to ensure the tip-over safety, safety-monitoring devices have been proposed. Therein pressures existing in the four hydraulic operated telescopes of the support legs are monitored. If the pressure drops off in two support leg cylinders, then the boom movement and the concrete pump are switched off. This technique can also be used in the case that the machine, for space reasons, is not fully supported (periodical BETON June 1996, page 362, 364). Research has however shown that pressure measurements in the telescoping cylinders of the support legs are not sufficient for a reliable monitoring of the support legs. This applies above all when one of the telescoping cylinders rests upon an abutment. Further, dynamic support effects cannot be detected with this monitoring system.